Arrays of antenna elements are often employed in both radar systems and sonar systems, the antenna elements of the sonar system taking the form of sonar transducers. The arrays my be utilized for the detection of a source of radiation, electromagnetic radiation in the case of radar and sonic radiation in the case of sonar, as well as for the indication of a direction of the source relative to the array. In both the cases of electromagnetic radiation and sonic radiation, the array receives radiation from sources of noise in addition to the signal emanating from a point distant from the array. The signal from the distant point is to be detected and the direction thereof is to be measured.
A situation of interest is that of a sonar array in the form of a line array wherein the broadside direction of the array is oriented in the general direction of a source of sound. As is well known, signals received by transducers in the right half of the array and signals received by transducers in the left half of the array may be processed by a bearing deviation indicator circuit to provide the bearing angle of a source of the sound relative to the array axis. Or, alternatively, the signals from the two halves of the array may be combined for detection of the presence of the sound source. In both cases, a problem exists in that noise, such as that customarily found within the ocean produces a lower limit on the magnitude of the received sound which can be detected and which can be measured to determine the direction. Attempts have been made to increase the signal power relative to the noise power by enlarging the sonar array. However, the resulting arrays are often too large to be employed on a ship which is to carry the sonar array.